Light propagation through a sharp-bend coupled-cavity waveguide in a two-dimensional photonic crystal

Abstract

We investigate light propagation through a coupled-defect waveguide with a $45\ifmmode^\circ\else\textdegree\fi{}$ sharp bend in a two-dimensional photonic crystal analytically and numerically. The waveguide mode is the degenerate defect state of a square lattice. The transmission through such a structure drops by two orders of magnitude if a $45\ifmmode^\circ\else\textdegree\fi{}$ bend is introduced. We show that, by properly distorting the lattice around each defect, the splitting of the degenerate defect state allows resonant transmission through the bend, leading to a two orders of magnitude increase in transmission through the bend waveguide. Several applications of such waveguides are discussed including dynamical directional switching and dynamic light trapping and releasing.